"Ultimate Weapon" idea

[RumoCrytuf]

I'm building a 100 Floor dungeon for my players (This is a long project, so I'm keeping them occupied with PoTA in the meantime). The story behind this dungeon is a race of dwarves who were made of stone a bled gold challenged the gods to a smithing contest. Two "Ultimate Weapons" were made. I need help on whether these two weapons would be too powerful for a lvl 15-20 group of players.

1st weapon: OmniBlade

Legendary Weapon (Requires attunement)

This weapon seems to be no more than an adamantine hilt of a sword. Upon speaking the command word as an action, the hilt turns into whatever the desired weapon the wielder desires. All attacks a treated as a +2 magical weapon Also, Each form has a special bonus for it.

Greatsword: Critical hits now occur on a natural 19 or 20. If the wielder can achieve this normally (such as skills or some such) It becomes a natural 18-20.

Longsword/Bastard Sword: Opportunity attacks may be taken with a -5 to the attack roll, attacks that succeed are automatic critical hits.

Spear: If the attack roll is ten or more than the AC of the target, the target takes an extra xd8 damage, where x is 1/5 the players level, rounded down, minimum of 1.

Whip: If the target is using a shield, disregard the shields AC bonus.

This is all I have right now, will post the second weapon later. If you have any suggestions for other weapon forms, let me know!

EDITS:

Changed Spear to 10 more AC instead of 5.

Crossbow form: This crossbow fires 3 bolts per attack, each bolt deals an additional 1d4 lightning damage. This weapon can only be fired once per turn.

Scythe: Attacks deal an extra 2d4 Necrotic damage. On a critical hit it heals the wielder for half.

Dagger: Attacks have a chance to poison the target (DC is 8+Proficiency+Dex modifier). On a success, the target takes 1d10+2 Poison damage and is poisoned.

Katana: On a critical hit, do not roll extra damage, instead the target makes a DC 4 Saving throw (No modifiers), on a failure, the target is instantly killed.



2nd Weapon:

Sol

Legendary Weapon (Spear) Requires atunement

This spear was forged inside of a dying star. It functions as a +5 spear and deals an extra 2d6 fire damage.

I know this spear doesn't seem as cool as the Omniblade, so I gave it an absurd bonus and a healthy chunk of extra damage.

[Sabeta]

That's pretty much Artifact Level with no drawbacks, but beyond that it's basically a Rod of Lordly Might, which is a +3 Mace with 6 buttons.
1) Becomes Flametongue
2) Becomes Battleaxe
3) Becomes Spear
4) Becomes 50-Foot Ladder (You determine the size, 50 is max)
5) Becomes Battering Ram (+10 Strength Versus Doors, Barricades, Etcetera)
6) Returns to normal, tells you where North is.
->Drain Life 1/Day (4d6 Necrotic Damage, Heals you for half)
->Paralyze 1/Day (1 Minute DC 17 Strength Check)
->Terrify 1/Day (All Creatures W/I 30 ft DC 17 Wisdom Check. Frightened Condition)

I would argue that, as immensely powerful as the Rod of Lordly Might is, that an extra 5% chance to crit, automatic crits, and ignoring shields are all a bit strong. The Spear form is just flat-out broken in my opinion. With 20 Strength at level 20 you have 5+2+6=13 chance to hit. Not even factoring in Advantage I can imagine that players are going to land that bonus very frequently, and if they crit it doubles.

All weapons like this do though is force you into increasing the health of your monsters though, if you're content with that then it's not really game breaking, just beware that this is indeed a high-power weapon.

[ruy343]

Who says that the weapon has to be wield-able?

In one campaign of mine, the villain's plan was to perfect an aerosolized anti-magic potion, and release it to the whole world. How was he going to release it? He found a dormant volcano, and rigged it to explode!

Best campaign moment ever: when the players realized what the villain was planning to do, after trying to piece it together for ten sessions. They were gloriously furious - in a righteous anger kind of way.



What if something like that was at the bottom of your dungeon: a weapon so terrible that it has been hidden away and kept secret for ages, because it's a force of nature that would lead to untold destruction? The fantasy equivalent of a nuclear weapon?